mysql日期格式化

1 select DATE_FORMAT(dtl.transdate,"%Y-%m-%d") as transdate,
2         right(DATE_FORMAT(concat(transdate,transtime),"%Y-%m-%d %H:%i:%s"),8) as
3         transtime,dtl.custname,dtl.stuempno,dtl.deviceid,dtl.devtype,dev.devicename,a.names as areaname
4         from t_devicedtl dtl
5         left join t_device dev on dev.deviceid=dtl.deviceid
6         left join t_area a on a.id=dev.areaid

1. DATE_FORMAT(dtl.transdate,"%Y-%m-%d") ：例如将数据库中的transdate字段20200123进行格式化，结果为：2020-01-23
2. DATE_FORMAT(concat(transdate,transtime),"%Y-%m-%d %H:%i:%s")：例如字段transdate:20200123,字段transtime:122359,结果为：2020-01-23 12:23:59
3. right(DATE_FORMAT(concat(transdate,transtime),"%Y-%m-%d %H:%i:%s"),8) :取格式化后取后8位，结果为：12:23:59